Bacterial fouling (biofouling in short, hereafter) is a serious problem in every aspect of our lives. Bacterial attachment to solid surfaces and colonization is the main source of bacterial infection. Medical devices, biomedical equipment, food packaging, and drinking water distribution systems are all susceptible to biofouling and pose potentially harmful impacts on human health. For example, urinary tract infection is the most common hospital associated infection and 80% are caused by biofouling in an indwelling urinary tract catheter. Another example is the biofouling on ships' hulls that is a primary cause of attachment of sea creatures, such as barnacles, algae, mussels, and shells, resulting in higher friction on the hulls. As a result, 30-50% more energy is consumed during sailing.
One of the methods to address this biofouling problem is to use antibiotic or bactericidal agents. In this method, antibiotic materials are either impregnated inside the wall of solid surface to be protected from bacterial colonization, or coated on the surface of it to prevent biofouling. In this case, antifouling agents diffuse out of the surface as they dissolve into the water and kill the bacteria near the surface. Many antifouling systems in current health-care products, water filtration, home appliances such as air conditioners, humidifiers, and air purifiers, and kitchen appliances are based on the diffusion of antibiotic (or bactericidal) agents from the contact surface. The biggest problem in this method is the rapid depletion of the antibiotic agent as it diffuses out and is removed from the surface. Besides, these antibiotic chemicals may be harmful to humans and environment. Furthermore, there are reports that bacteria develop antibiotic resistance to these chemicals. Common diffusion-based agents currently used in the market are triclosan, triclocarban, Trichlorocarbamidem, chloroxylenol, nitrofurazone and organic silver. Silver coating is gaining much attention as an alternative to traditional bactericides. Again, the coating loses its effect in a short time period. Silver coatings are expensive, and their antifouling effect is controversial. In one study, silver-impregnated catheters were associated with more frequent bacteriuria and an increased risk of staphylococcal bacteriuria. Conclusively silver coatings may diminish bacteriuria for a few days but are costly and have no role in long-term prevention.
There are non-diffusion-based antifouling methods that use surface structure modifications with various polymeric materials. Chemicals that are being used or investigated are polyethylene glycol, poly(2-hydroxyethyl methacrylate), i.e., PHEMA, and furanones. Although these materials last longer on solid surfaces than the diffusion-based agents, their efficacies are not sufficient to outweigh their costs. For example, to form PHEMA brushes on a solid surface, atom transfer radical polymerization has to be performed on the silanized surface. This type of coating process is not simple, and costly. Further, there remains uncertainty of the coating's mechanical durability and its effectiveness in preventing biofouling.
In another category of antifouling strategies, there are physical methods that use sonication, UV light, and electrical pulse. These methods are more effective in removing the bacterial colonies already formed on the surface rather than preventing the cell attachment. However, these physical methods have many limitations that overshadow their efficacy and durability. The bacteria contaminated area that sonication and UV light can be applied is limited because ultrasound and UV light can only be applied to a small area with a short penetration depth. They are inconvenient to use due to accompanying auxiliary devices such as sonnicator, UV generator, batteries, etc. Moreover, in the case of using them inside human body, it is highly suspected they may be harmful to human body cells. Periodic electrical pulse was reported effective in preventing biofouling and also effective to remove already formed biofilms. Electric pulse only travels through conductive materials and this requirement also restricts its application as well as other requirements such as a pulse generator, controller, and batteries.
The present invention is based on the effect of electrical current on preventing bacterial adhesion. As demonstrated in electrical pulse generators, applying electrical current to the surface of concern is regarded a plausible way to protect the surface from biofouling. Because the electrical current is generated by the movement of fluid over the surface of the coating agent, it does not require a pulse generator, batteries, or any other auxiliary devices. Because it consists of cross-linked polymers and magnetic particles, it forms a durable coating that lasts a very long time. This coating has another potential advantage that protects surfaces from chemical corrosion.